(1) Field of the Invention
The present invention relates to a preferable document feeder attached to an image forming apparatus such as copiers and the like. More specifically, the present invention is directed to an image forming apparatus equipped with a document feeder which automatically feeds an original document inserted from the outside to deliver it to an image forming station in an image forming apparatus and automatically discharges the document outside after a predetermined process is effected inside the image forming apparatus.
(2) Description of the Prior Art
In an image forming apparatus such as copiers, a copy document is placed on a transparent original table and then covered by an original cover. Then, as the operator starts the copying switch, a duplicated image of the original placed is reproduced on a sheet of paper as is conveyed in a proper manner.
In this case, if the copy original is of sheet-like material, it is troublesome to handle the document manually and place it on the original table. To deal with this, some copiers have an automatic document feeder on the top of the original table. That is, this document feeder has a document tray on which sheet-like original documents are placed and automatically delivers the sheet document by means of a paper feeding means. The document feeder successively feeds original documents placed on the document tray, one by one, from the topmost or lowermost sheet, in accordance with instructions from the copier body and delivers it to a station where the original is exposed to light. After the exposure, the feeder discharges the original to a document discharging tray. Since the document feeder is thus constructed, the apparatus becomes markedly large-sized and expensive.
Hence, when the automatic document feeder is attached to the copier body, the cost naturally becomes increased. In a case where one or some documents are to be copied, the use of automatic document feeder, rather takes time for copying a first document because the operator should set the document or documents on the document tray and then wait for the operation to start until both the copier and the document feeder become ready to make synchronism with one another. Accordingly, the automatic document feeder takes as much time as operator's manual handling of documents, if the number of documents to be copied is few.
Accordingly, in order to effect reduction in cost and other purpose, an automatic document feeder as shown in FIG. 1 has been proposed in Japanese Patent Application Laid-Open Hei 6 No.67,497. This document feeder has two exposure portions, or includes, in addition to a typical original table on which a document is placed and exposed to light to effect image forming, a separate exposure station to which a sheet original is inserted and conveyed one by one. In the figure, the document feeder designated at 102 is attached to an original cover 126 pivotably supported by a shaft 125, and includes: a document tray 130 utilizing the top face of the original cover 126; a drawing roller 131 for pulling a document D from the document tray 130; a feed roller 132; a guide plate 133 for guiding the document D to an exposure portion A on one side of an exposure glass 120; and a discharging roller 136 for conveying the original D from the exposure portion A.
In this arrangement, as the document feeder 102 starts to operate, a document D is fed from the document tray 130 and conveyed by a platen roller 134 and a driven roller 137 as nipped between the rollers. Then, the document D are passed through the discharging roller 136 and discharged to the output tray 135. In the meantime, in an optical system 121, a copy lamp 122 is moved right below the platen roller 134 and positioned at that place while the document D is moved through the exposure area A on the exposure glass 120 and copied.
In a normal copying operation where a document D is placed on the transparent original table 120 for image exposure and scanned by moving the optical system 121 along the exposure glass 120 to make a copy, the copy lamp 122 and the like are driven in response to a copy start signal to a position where exposure is to be made and then starts scanning in an exposure area B from the left to the right in the figure to complete a copy.
In the above document feeder disclosed in Japanese Patent Application Laid-Open Hei 6 No.67,497, since the original cover over the exposure glass serving as an original table is used to deliver documents successively to the exposure station, the cost can be more or less reduced.
Nevertheless, since the different exposure area A is provided separately from the normal exposure area B so that the document from the document feeder is exposed in the exposure area A, the optical system must be controlled to move from the exposure position where the document is conveyed to the exposure position where the document is placed on the original table 120. Accordingly, the document feeder of this type also becomes complicated in structure and large-sized as the conventional automatic document feeder. Further, the document feeder requires both the document tray and the discharge tray for conveying documents from the former to the latter. In this respect, the document feeder is the same as the conventional automatic document hander, resulting in increased cost for that part.